On a warm spring day in 1975, sisters Sheila and Katherine Lyon left Wheaton Plaza and walked toward their Plyer’s Mill Road home. They never arrived, vanishing somewhere in Kensington Heights.

The most vexing disappearance in Montgomery County history, the case has been recounted in the National Enquirer and generated hundreds of leads, all of which have culminated in dead ends.

On March 25, 1975, Sheila, 12, and her younger sister Katherine, 10, walked along Drumm Avenue and over to Wheaton Plaza to view the Easter displays at the mall and have lunch at the Orange Bowl restaurant. Their older brother saw them in the Orange Bowl eating pizza together around 2 p.m.

Longtime Kensington Heights resident James Mann may have been one of the last to see the two girls. He recalls waving to them as they passed his house on the corner of Drumm Avenue and Devin Place that afternoon. He said they continued down Drumm toward McComas.

According to the Missing Persons Cold Case Network, a volunteer-based Web site profiling 3,000 missing persons cases, a friend of the girls also placed the girls near Drumm and Devin Place.

Back in 1975, Mann recalled that there was a large wooded area with a cut-through path connecting the two segments of Drumm. Drumm Court and the newer houses on Drumm were years away from being built.

Police and neighbors fanned out across Kensington Heights searching for clues. Mann recalls that police asked permission to search his crawl space, along with those of his neighbors. They also checked the sewer drain on Drumm and dove in the pond at what was then the Kensington Gardens Nursing home.

“I wanted to help them in any way I could,” he said. “It was such a tragedy.”

Police ruled out the possibility that the girls had run away because they were younger than most runaways, who are usually found or return within 24 hours. The girls had less than $2 each when they left home and did not take any extra clothing with them.

Acting on a tip from a psychic, 135 national guardsmen, as well as a contingent of Montgomery County police combed two square miles of parkland midway between Laytonville and Olney in search of the girls, but never found a clue.

One lead given to police was from mall patrons, who saw the girls talking with a tall, white man in a brown suit. The man, thought to be in his 50s, was carrying a briefcase and taped their conversation. Police released a sketch of the man, but he never has been found.

A witness in Manassas, Virginia reported seeing two girls resembling Sheila and Katherine bound and gagged in the rear of a beige Ford station wagon on April 7, 1975. The driver of the station wagon resembled the man seen questioning children at the mall. When the driver spotted the witness tailing him, he ran a red light and sped away.

In 1987, Montgomery County Police said that the Lyon sisters’ disappearance may be linked to a Virginia man who was suspected in sexual molestations and slayings of children in at least three states.

The man, Fred Howard Coffey Jr., was in Montgomery County near Wheaton Plaza on April 1, 1975, seven days after the Lyon girls vanished. He is now serving a life sentence in North Carolina for murder and child molestation. In other cases in which Coffey was a prime suspect, victims have been lured by a man using devices including a fishing pole and a metal detector, raising the possibility that the tape recorder was another such device. He has never been charged in the Lyon sisters case.

During the disappearance and for years afterward, on the anniversary of the girls’ disappearance, newspapers have run stories, with headlines like “Desperate Hunt,” in a front-page story in the Washington Post two weeks after the girls were reported missing. None of the articles interviewed Kensington Heights residents, beyond John Lyon, the girls' father.

"They weren't shy," Lyon said in an interview with the Montgomery Journal. "They were very confident and trusting. Maybe too much."

"I've been hanging in limbo," Lyon said in the story written in 2000, on the 25th anniversary of the girls’ disappearance. "But you learn to do that. You learn how to live your life again."

Lyon, a former disc jockey at WMAL-AM (630), joined the Montgomery County Victim Assistance and Sexual Assault Program in 1992. Lyon said the chance to help other victims has helped him. "You can still stand upright and move on," Lyon said. "It helps to know someone out there has been through this kind of ordeal, too."

As a victim assistant, Lyon had a chance to the 1999 trial of Hadden Clark, who was convicted of murdering 6-year-old Michele Dorr, who was reported missing from her father's Silver Spring home on May 31, 1986. The Journal reported, “At times, Lyon thought to himself, ‘This could be my trial.’”

One of the sisters’ brother Jay, who was 15 at the time of the disappearance is 43 years old now and a homicide detective with the Montgomery County police.

According to a 1998 Washington Post article, “On the 23rd anniversary of the girls' disappearance, Lyon, his wife, Mary, their two grown sons and five grandchildren planted a weeping cherry tree and small flower garden in a local cemetery. Nearby, they placed a stone marker etched with Sheila's and Katherine's names, their birthdays and the day they vanished. They visit once a week.

“‘It's unbelievable that people can disappear off the face of the Earth without a trace when they find dinosaur bones and identify them,’ Lyon says. ‘But maybe it's God's plan or something. If it's something you could understand, then it would be easier to tell you how we get through it.’”